TUI flight TOM-24 was en route between London Gatwick Airport to Bridgetown in Barbados when its crew was forced to divert to Shannon airport.
An elderly woman, believed to be in her 70s, was found unresponsive, prompting a medical emergency.
The aircraft, a Boeing 787-900 Dreamliner, diverted to Shannon, where it was met by paramedics who took the ill passenger to hospital.